GZ5.I3 
C  7  Sere 

1501 


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COOPER 


GENERAL  SPECIFICATIONS 
FOR  STEEL  HIGHWAY  AND 
ELECTRIC  RAILWAY 
BR I DGES 


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“  The  most  perfect  system  of  rules  to  insure  success  must 
be  interpreted  upon  the  broad  grounds  of  professional  mtelh- 
gence  a,nd  common  sense. 


GENERAL  SPECIFICATIONS 


FOR 


STEEL  HIGHWAY  AHD  ELECTRIC  RAILWAY 
BRIDGES  AHD  YIADDCTS.  If 


NEW  AND  REVISED  EDITION, 

1901. 


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By  THEODORE  COOPER: 

Consulting  Engineer. 


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VOLUME. 

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Accession  No. 


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By  THEODORE  COOPER,  M.  Am.  Soc.  C.  E. 

Specifications  for  Steel  Railroad  Bridges,  1901,  .  .  $0  50 


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American  Railroad  Bridges  (reprint  from  Transac¬ 
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July,  1889),  60  pages,  8vo,  cloth,  .  .  .  .  2  00 


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Copyright  by  Theodore  Cooper 

Consulting  Engineer,  35  Broadway,  New  York. 


General  Specifications  for  Steel  Highway 
and  Electric  Railway  Bridges 
and  Viaducts. 


FIFTH  EDITION. 

1901. 


GENERAL  DESCRIPTION. 

Bridges  under  these  specifications  are  divided  into  six  classes, 
classes,  for  different  localities  and  various  loadings,  as  fol¬ 
lows  :  (§  38.) 

Class  Ai.  City  bridges  having  buckle-plate  floors  and  an 
accepted  form  of  paving  resting  on  a  concrete  base.  (§  29.) 

Class  A2.  City  bridges  having  plank  flooring.  (§  29.) 

Class  B.  Suburban  bridges  or  Interurban  bridges  carry¬ 
ing  heavy  electric  cars.  (§  29.) 

Class  C.  Town  or  country  bridges  carrying  light  elec¬ 
tric  cars  or  bridges  carrying  heavy  loads  from  quarries  or 
manufactories. 

Class  D.  Country  bridges  carrying  only  ordinary  high¬ 
way  traffic. 


2 


Class  Ei.  Bridges  carrying  heaviest  motor  cars,  only. 
Class  E2.  Bridges  carrying  light  motor  cars,  only. 


i.  All  parts  of  the  structures  shall  be  of  wrought  steel, 
except  the  flooring,  floor  joists  and  wheel  guards,  when 
wooden  floors  are  used.  Cast-iron  or  cast-steel  may  be 
used  in  the  machinery  of  movable  bridges,  for  wheel 
guards,  and  in  special  cases  for  bed-plates. 

Kind  of  Girders.  2.  The  following  kinds  of  girders  shall  preferably  be 
employed  : 

Spans,  up  to  25  feet _ Rolled  beams. 

“  20  to  40  “  _ Rolled  beams  or  plate  girders. 

“  40  to  80  “  _ Riveted  plate  or  lattice  girders. 

“  80  to  120  “  _ Lattice  girders. 

“  over  120  “  _ Lattice  or  pin-connected  trusses. 

Length  of  span.  In  calculating  strains  the  length  of  span  shall  be  under¬ 
stood  to  be  the  distance  between  centres  of  end  pins  for 
trusses,  c.  to  c.  of  trusses  for  cross  floor  beams,  and  be¬ 
tween  centres  of  bearing  plates  for  all  longitudinal  beams 
and  girders. 

Trusses^  3-  Unless  otherwise  specified,  the  form  of  bridge  trusses 
may  be  selected  by  the  bidder  ;  for  through  bridges,  the 
end  vertical  suspenders  and  two  panels  of  the  lower  chord, 
at  each  end,  will  be  made  rigid  members.  In  through 
bridges,  the  floor  beams  shall  be  riveted  to  the  posts,  above 
or  below  the  pins. 

Lateral  Bracing.  4-  All  lateral,  sway  and  portal  bracing  must  be  made  of 
shapes  capable  of  resisting  compression  as  well  as  tension, 
and  must  have  riveted  connections.  All  bridges  must  have 
lateral  struts  at  the  ends,  except  where  end  floor  beams  act 
as  such. 

Trestle  Towers.  5.  Each  trestle  bent  shall,  as  a  general  rule,  be  composed 

of  two  supporting  columns,  and  the  bents  united  in  pairs  to 

form  towers;  each  tower  thus  formed  of  four  columns  shall 

♦ 

be  thoroughly  braced  in  both  directions,  and  have  struts 
between  the  feet  of  the  columns.  The  feet  of  the  columns 


<"iv  I  Eu*  29  0  '01  McCHitrg.  4 0 


3 


must  be  secured  to  an  anchorage  capable  of  resisting 
double  the  specified  wind  forces.  (§  40.) 

6.  Each  tower  shall  have  sufficient  base,  longitudinally, 
to  be  stable  when  standing  alone,  without  other  support 
than  its  anchorage.  (§§  40,  43.) 

7.  Tower  spans  for  high  trestles  shall  not  be  less  than  30 
feet. 

8.  Where  footwalks  are  required,  they  will  generally  be  Foot-walks, 
placed  outside  of  the  trusses  and  supported  on  longitudinal 
beams  resting  on  overhanging  steel  brackets. 

9.  A  strong  and  suitable  handrailing  will  be  placed  at  Railing, 
each  side  of  the  bridge  and  be  rigidly  attached  to  the  su¬ 
perstructure. 

10.  For  all  through  bridges  there  shall  be  a  clear  head- Head -room, 
room  of  15  feet  above  the  floor,  for  Classes  A,  B,  C  and  E; 

and  a  minimum  head-room  of  12^3  feet  for  Class  D. 

11.  In  comparing  different  proposals,  the  relative  cost  of  Proposals, 
the  required  masonry  or  changes  in  existing  work  will  be 
taken  into  consideration. 

12.  Contractors  in  submitting  proposals  shall  furnish 
complete  strain  sheets,  general  plans  of  the  proposed 
structures,  and  such  detail  drawings  as  will  clearly  show 
the  dimensions  of  all  the  parts,  modes  of  construction  and 
the  sectional  areas. 

13.  Upon  the  acceptance  of  the  proposal  and  the  execu¬ 
tion  of  contract,  all  working  drawings  required  by  the  En¬ 
gineer  must  be  furnished  free  of  cost. 

14.  No  work  shall  be  commenced  or  materials  ordered  Approval  of 

.  .  Plans. 

until  the  working  drawings  are  approved  by  the  Engineer 
in  writing;  if  such  working  drawings  are  detained  more 
than  one  week  for  examination,  the  Contractor  will  be 
allowed  an  equivalent  extension  of  time. 

FLOOR  SYSTEM. 

15.  All  cross  floor  beams  will  be  rolled  or  riveted  steel  Floor  Girders, 
girders,  rigidly  connected  to  the  trusses  at  the  panel 
points. 

16.  All  longitudinal  girders  of  bridges  of  Classes  Ai  and 


4 


A 2  will  be  of  steel ;  all  track  stringers  of  bridges  of  Classes 
B,  C  and  E  will  be  of  steel.  Unless  otherwise  specified  all 
other  longitudinal  girders  of  Classes  B  and  C  will  be  of 
steel.  The  longitudinal  girders  of  bridges  of  Class  D  may 
be  either  of  wood  or  steel.  When  the  longitudinal  beams 
are  of  steel,  they  must  be  securely  fastened  to  the  cross 
floor  beams. 

Country  Bridges. 


wooden  Floor,  17.  Wooden  floor  joists  will  be  spaced  not  over  2  feet 
centres,  and  will  lap  by  each  other,  so  as  to  have  a  full 
bearing  on  the  floor  beams,  and  will  be  separated  -J  inch  for 
free  circulation  of  air.  Their  scantling  will  vary  in  ac¬ 
cordance  with  the  length  of  panels  selected,  but  shall  never 
be  less  than  3  inches,  or  one-fourth  of  depth  in  width. 
When  spaced  not  over  2-foot  centres,  one  joist  shall  be 
considered  as  carrying  only  two-thirds  of  the  concentrated 
live  load. 

18.  The  floor  plank  shall  be . . inches  thick,  laid  with 

|-inch  openings,  and  spiked  to  each  supporting  joist. 
When  this  is  to  be  covered  with  an  additional  wearing 
floor  (§  19),  it  must  be  laid  diagonally  and  with  -J  inch 
openings;  all  plank  shall  be  laid  with  the  heart  side 
down.  The  floor  plank  must  have  a  thickness,  in  inches , 
at  least  equal  to  the  distance  apart  of  these  beams,  in  feet , 
with  a  minimum  thickness  of  2\  inches.  The  floor  plank 
must  bear  firmly  upon  the  beams  and  be  securely  fastened 
to  the  same. 

19.  Where  specified  an  additional  wearing  floor  ij  inches 
thick  of  white  oak  plank  shall  be  placed  over  the  above. 
(§  is.) 


Allowed  strain 
on  Timber. 


20.  The  footwalk  plank  will  be  2  inches  thick  and  not 
over  6  inches  wide,  spaced  with  a  inch  openings. 

21.  There  will  be  a  wheel  guard,  of  a  scantling  not  less 
than  6x4,  on  each  side  of  the  roadway  to  prevent  the  hubs 
of  wheels  striking  any  part  of  the  bridge.  It  should  be 
blocked  up  from  the  floor  to  admit  drainage  and  ventilation. 

22.  The  maximum  strain  allowed  upon  the  extreme  fibre 
of  the  joist  will  be  1,200  pounds  per  square  inch  on  yellow 


* 


5 


pine  and  white  oak,  and  1,000  pounds  per  square  inch  on 
white  pine  and  spruce. 

City  Bridges. 

23.  Buckle-plates  will  be  not  less  than  T5g-  inch  thick  and  Buckie  piates. 
will  crown  2  inches  at  the  centre.  Plates  of  this  thickness 

and  crown  may  be  used  to  widths  of  4  feet  under  the  road¬ 
way  and  5  feet  under  the  footwalks.  (§§  93-96.) 

24.  Bridges  with  buckle  plate  floors  will  have  a  suitable  Curbs  and 

0  .  1  .  Guards. 

metal  curb  on  each  side  of  the  roadway  to  hold  paving  and 
act  as  a  wheel  guard.  The  wheel  guard  must  be  so  ar¬ 
ranged  that  it  can  be  removed  and  replaced  when  worn  or 
injured.  There  will  also  be  a  metal  edging  strip  on  each 
side  of  the  footwalks  to  hold  the  paving  in  place. 

25.  The  concrete  over  buckle-plates  shall  be  at  least  3  Concrete, 
inches  thick  on  the  roadway  and  2  inches  thick  on  the  side¬ 
walks,  over  the  highest  point  to  be  covered,  not  counting 
rivet  heads. 

26.  The  sidewalks  shall  slope  1  inch  in  5  feet,  preferably 
towards  the  roadway.  The  roadway  shall  crown  from  curb 
to  centre  1  inch  for  each  10  feet  of  the  roadway  width. 

The  depth  of  the  curb  will  be  6  inches. 

27.  The  subgrade,  top  of  concrete,  for  the  sidewalks  will 

be _ inches  below  final  grade  and  slope. 

The  concrete  over  roadway  will  be  laid  to  the  correct 

crowning  and  elevation  to  allow . inches  for  the  selected 

paving. 

28.  Scuppers  must  be  provided  at  frequent  intervals  along  Scuppers, 
the  curbs  or  wheel  guards  for  drainage  and  for  passing 

the  sweepings  and  snow,  clear  from  contact  with  any  parts 
of  the  tracks  or  floor  system. 

29.  Classes  A  and  B  shall  be  designed  to  carry  at  any  Double  Track, 
future  time  a  double-track  electric  railway. 

Electric  Railway  Bridges. 

30.  The  wooden  floors  will  consist  of  transverse  ties  or  wooden  Floor, 
floor  timbers;  their  scantling  will  vary  in  accordance  with 


6 


the  design  of  the  supporting  steel  floor.  (§  22.)  They  shall 
be  spaced  with  openings  not  exceeding  six  inches,  and  shall 
be  notched  down  y2  inch  and  be  secured  to  the  supporting 
girders  by  f-inch  bolts  at  distances  not  over  six  feet  apart. 
For  deck  bridges  the  ties  will  extend  the  full  width  of  the 
bridge,  and  for  through  bridges  at  least  every  other  tie 
shall  extend  the  full  width  of  bridge  fora  footwalk. 

Guard  Timbers.  31.  There  shall  be  a  guard  timber  (scantling  not  less  than 
5  x  7")  on  each  side  of  each  track,  with  its  inner  face  parallel 

to  and  at _ feet . inches  from  centre  of  track.  Guard 

timbers  must  be  notched  one  inch  over  every  floor  timber, 
and  be  spliced  over  a  floor  timber  with  a  half  and-half  joint 
of  six  inches  lap.  Each  guard  timber  shall  be  fastened  to 
every  third  floor  timber  and  at  each  splice  with  a  three- 
quarter  (|)  inch  bolt.  All  heads  or  nuts  on  upper  faces  of 
ties  or  guards  must  be  countersunk  below  the  surface  of 
the  wood.  (§  76.) 

32.  The  guard  and  floor  timbers  must  be  continuous  over 
all  piers  and  abutments. 

33.  The  floor  timbers  from  centre  to  each  end  of  span 
must  be  notched  down  over  the  longitudinal  girders  so  as  to 
reduce  the  camber  in  the  track,  as  directed  by  the  Engineer. 

34.  All  the  floor  timbers  shall  have  a  full  and  even  bearing 
upon  the  stringers  ;  no  open  joints  or  shims  will  be  allowed. 

35.  On  curves  the  outer  rail  must  be  elevated,  as  may  be 
directed  by  the  Engineer. 

cieat  width.  36.  In  all  through  bridges  the  clear  width  from  the  centre 
of  the  track  to  any  part  of  the  trusses  shall  not  be  less  than 
seven  (7)  feet  at  a  height  exceeding  one  foot  above  the  rails 
where  the  tracks  are  straight,  and  an  equivalent  clearance, 
where  the  tracks  are  curved. 

37.  The  standard  distance,  centre  to  centre  of  tracks  on 

straight  lines,  will _ feet. 

LOADS. 

38.  All  the  structures  shall  be  proportioned  to  carry  the 
following  loads: 

1  st.  The  weight  of  metal  in  the  structure  and  floor. 


7 


♦ 


2d.  The  weight  of  the  paving  and  concrete  or  the 
wooden  floor,  considering  each  foot  of  board  measure  to 
weigh  4J  pounds  for  oak  and  other  hard  woods,  and  31- 
pounds  for  spruce  and  white  pine. 

These  two  items,  taken  together,  shall  constitute  “  the  Dead  Load, 
dead  load.” 

3d.  A  “  live  ”  or  moving  load,  according  to  one  of  the  Live  Loads, 
following  classes: 

Class  Ai  and  Class  A2. — City  Bridges  : 

For  the  floor  and  its  supports,  on  any  part  of  the  road¬ 
way  or  on  each  of  the  street  car  tracks,  a  concentrated  load 
of  24  tons  on  two  axles  10  feet  centres  (assumed  to  occupy 
12  feet  in  width  for  a  single  line  and  22  feet  for  a  double 
line),  and  upon  the  remaining  portion  of  the  floor,  including 
footwalks,  a  load  of  100  pounds  per  square  foot. 

For  the  trusses,  loads  as  per  Table  A. 

Class  B. — Suburban  or  Interurban  Bridges: 

For  the  floor  and  its  supports,  on  any  part  of  the  road¬ 
way,  a  concentrated  load  of  12  tons  on  two  axles  10  feet 
centres  or  on  each  of  the  street  car  tracks  a  concentrated 
load  of  24  tons  on  two  axles  10  feet  centres  ;  and  upon  the 
remaining  portion  of  the  floor,  including  footwalks,  a  load 
of  100  pounds  per  square  foot  of  floor. 

For  the  trusses,  loads  as  per  Table  A. 

Class  C.— (Class  B2  of  former  editions) : 

For  the  floor  and  its  supports,  on  any  part  of  the  road¬ 
way,  a  concentrated  load  of  12  tons  on  two  axles  10  feet 
centres,  or  on  street  car  track  a  concentrated  load  of  18 
tons  on  two  axles  10  feet  centres  ;  and  upon  the  remaining 
,  portion  of  the  floor,  including  footwalks,  a  load  of  100 
pounds  per  square  foot  of  floor. 

For  the  trusses,  loads  as  per  Table  A. 

Class  D. — (Class  C  of  former  editions.)  Country  High¬ 
way  Bridges  : 

For  the  floor  and  its  supports,  a  load  of  80  pounds  per 
square  foot  of  total  floor  surface,  or  6  tons  on  two  axles  10 
feet  centres. 

For  the  trusses,  loads  as  per  Table  A. 


8 


Class  Ei. — Electric  Railway  Bridges,  with  Heavy  Equip¬ 
ment  : 

For  the  floor  and  its  supports,  a  load  of  24  tons  on  two 
axles  10  feet  centres,  on  each  track. 

For  the  trusses,  loads  as  per  Table  A. 

Class  E2. — Electric  Railway  Bridges,  with  Light  Equip¬ 
ment  : 

For  the  floor  and  its  supports,  a  load  of  18  tons  on  two 
axles  10  feet  centres,  on  each  track. 

For  the  trusses,  loads  as  per  Table  A. 

TABLE  A. — Live  Loads  for  the  Trusses. 


Class  A. 


Span  in  feet. 

Pounds  per 
lineal  foot  of 
each  car 
track. 

Pounds  per 
square  foot 
of  remaining 
floor  surface. 

Up  to 

100 . 

1  800 

100 

105 . 

1  770 

99 

110 . 

1  740 

98 

115 . 

1  710 

97 

120 . 

1  680 

96 

125 . 

1  650 

95 

130 . 

1  620 

94 

135 . 

1  590 

93 

140 . 

1  560 

92 

145 . 

1  530 

.  91 

150 . 

1  500 

90 

155 . 

1  470 

89 

160 . 

1  440 

88 

165 . 

1  410 

87 

170 . 

1  380 

86 

175 . 

1  350 

85 

180 . 

1  320 

84 

185 . 

1  290 

83 

190 . 

1  260 

82 

195  . 

1  230 

81 

200  and  over. . . 

1  200 

80 

Class  B. 

Span  in  feet. 

Pounds  per 
lineal  foot  of 
each  car 
track. 

Pounds  per 
square  foot 
of  remaining 
floor  surface 

Up  to 

100 . 

1  800 

80 

105 . 

1  770 

79 

no- . 

1  740 

78 

115 . 

1  710 

77 

120 . 

1  680 

76 

125 . 

1  650 

75 

130 . 

1  620 

74 

135 . 

1  590 

73 

140 . 

1  560 

72 

145 . 

1  530 

71 

150 . 

1  500 

70 

155  . 

1  470 

69 

160 . 

1  440 

68 

165 . 

1  410 

67 

170 . 

1  380 

66 

175 . 

1  350 

65 

180 . 

1  320 

64 

185 . 

1  290 

63 

190 . 

1  280 

62 

195 . 

1  230 

61 

200  and  over. 

1  200 

60 

Class  C. 


Up  to 

100 . 

1  200 

80 

105 . 

1  190 

79 

110 . 

1  180 

78 

115 . 

1  170 

77 

120 . 

1  160 

76 

125 . 

1  150 

75 

130 . 

l  140 

74 

135 . 

1  130 

73 

140 . 

l  120 

72 

145 . 

1  110 

71 

150 . 

1  100 

70 

155 . 

1  090 

69 

160 . 

1  080 

68 

165 . 

1  070 

67 

170 . 

1  060 

66 

175 . 

1  050 

65 

180 . 

1  040 

64 

185 . 

1  030 

63 

190 . 

1  020 

62 

195 . 

1  010 

61 

200  and  over. 

1  000 

60 

9 


TABLE  A  ( Continued ) — Live  Loads  for  the  Trusses. 


Class  D. 

Class  E  1. 

Class  E  2. 

Span  in  feet. 

Pounds  per 
square  foot 
of  floor 
surface. 

Span  in  feet. 

Pounds  per 
lineal  foot  of 
each  car 
track. 

Span  in  feet. 

Pounds  per 
lineal  foot  of 
each  car 
track. 

Up  to 

Up  to 

Up  to 

75 . 

80 

100 . 

1  800 

100.;*. . 

1  200 

80 . 

79 

105 . 

1  770 

105 . 

1  190 

85 . 

78 

110 . 

1  740 

110 . 

1  180 

90 . 

77 

115 . 

1  710 

115 . 

1  170 

95 . 

76 

120 . 

1  680 

120 . 

1  160 

100 . 

75 

125 . 

1  650 

125 . 

1  150 

105 . 

74 

130 . 

1  620 

130 . 

1  140 

110 . 

73 

135 . 

1  590 

135 . 

1  130 

115 . 

72 

140 . 

1  560 

140 . 

1  120 

120 . 

71 

145 . 

1  530 

145 . 

1  110 

125 . 

70 

150 . 

1  500 

150 . 

1  100 

130 . 

69 

155 . 

1  470 

155 . 

1  090 

135 . 

68 

160 . 

1  440 

160 . 

1  080 

140., . 

67 

165 . 

1  410 

165 . 

1  070 

145 . 

66 

170 . 

1  380 

170 . 

1  060 

150 . 

65 

175 . 

1  350 

175 . 

1  050 

155 . 

64 

180 . 

1  320 

180 . 

1  040 

160 . 

63 

185 . 

1  290 

185....:..:::: 

1  030 

165 . 

62 

190 . 

1  260 

190 . 

1  020 

170 . 

61 

195 . 

1  230 

195 . 

1  010 

175 . 

60 

200  and  over. 

1  200 

200  and  over. 

1  000 

180 . 

59 

185 . 

58 

190 . 

57 

195 . 

56 

200  and  over. 

55 

1 

The  maximum  strains  due  to  all  positions  of  either  of  the 
above  “  live  loads,”  of  the  required  class,  and  of  the  “  dead 
loads,”  shall  be  taken  to  proportion  all  the  parts  of  the 
structure. 

39.  To  provide  for  wind  strains  and  vibrations,  the  top  wind  Bracing 
lateral  bracing  in  deck  bridges,  and  the  bottom  lateral  brac¬ 
ing  in  through  bridges,  shall  be  proportioned  to  resist  a 
lateral  force  of  300  pounds  for  each  foot  of  the  span  ;  150 
pounds  of  this  to  be  treated  as  a  moving  load. 

The  bottom  lateral  bracing  in  deck  bridges,  and  the  top 
lateral  bracing  in  through  bridges,  shall  be  proportioned  to 
resist  a  lateral  force  of  150  pounds  for  each  lineal  foot. 

For  spans  exceeding  300  feet,  add  in  each  of  the  above 
cases  10  pounds  additional  for  each  additional  30  feet. 

40.  In  trestle  towers  the  bracing  and  columns  shall  be 
proportioned  to  resist  the  following  lateral  forces,  in 
addition  to  the  strains  from  dead  and  live  loads: 


10 


The  trusses  loaded  or  unloaded,  the  lateral  pressures 
specified  above  ;  and  a  lateral  pressure  of  ioo  pounds  for 
each  vertical  lineal  foot  of  the  trestle  bents. 

Temperature.  41.  Variation  in  tem  peratu  re,  to  the  extent  of  i5odegrees, 
shall  be  provided  for. 

centrifugal  42.  For  electric  railways  on  curves,  the  additional  effects 
due  to  the  centrifugal  force  of  cars  single  or  coupled  shall 
be  considered  as  a  live  load.  It  will  be  assumed  to  act  5 
feet  above  base  of  rail,  and  will  be  computed  for  a  speed  of 
40  miles  per  hour. 

Longitudinal  43.  The  strains  produced  in  the  bracing  of  the  trestle 
towers,  in  any  members  of  the  trusses,  or  in  the  attach¬ 
ments  of  the  girders  or  trusses  to  their  bearings,  by  sud¬ 
denly  stopping  the  maximum  electric  car  trains  on  any  part 
of  the  work  must  be  provided  for;  the  coefficient  of  friction 
of  the  wheels  on  the  rails  being  assumed  as  0.20. 

44.  All  parts  shall  be  so  designed  that  the  strains  coming 
upon  them  can  be  accurately  calculated. 

PROPORTION  OF  PARTS. 

Tensile  Strain.  45.  All  parts  of  the  structures  shall  be  proportioned  in 
tension  by  the  following  allowed  unit  strains: 

Medium  Steel.  For  Medium  Steel.  Pounds  per 

square  inch. 

Floor  beam  hangers,  and  other  similar  members 

liable  to  sudden  loading,  net  section . .  8,000 

Longitudinal,  lateral  and  sway  bracing,  for  wind 

and  live  load  strains  (§§  6,  39,  40) _  18,000 

Solid  rolled  beams,  used  as  cross  floor  beams  and 

stringers _ _  13,000 

Bottom  flanges  of  riveted  girders,  net  section _  13,000 

Bottom  chords,  main  diagonals,  counters  live^ioads.  dead°ioads. 
and  long  verticals . .  12,500  25,000 

For  swing  bridges  and  other  movable  structures,  the  dead 
load  unit  strains,  during  motion,  must  not  exceed  three- 
fourths  of  the  above  allowed  unit  strains  for  dead  load  on 
stationary  structures. 

Soft  steel.  Soft  Steel  may  be  used  in  tension  with  unit  strains  ten 
per  cent,  less  than  those  allowed  for  Medium  Steel. 


11 


46.  Angles  subject  to  direct  tension  must  be  connected 
by  both  legs,  or  the  section  of  one  leg  only  will  be  con¬ 
sidered  as  effective. 

4 7.  In  members  subject  to  tensile  strains  full  allowance  Net  section, 
shall  be  made  for  reduction  of  section  by  rivet-holes,  screw- 
threads,  etc.  (§§  75,  79.) 

48.  Compression  members  shall  be  proportioned  by  the  c^Prsessive 
following  allowed  unit  strains: 

For  Medium  Steel . 

I  Medium  Steel. 

Chord  segments  P=  12,000 — 55—for  live  load  strains. 

r 

P==  24,000 — 1  io— for  dead  load  strains. 

r 


All  posts  of  ^ 

through  P=\o,ooo — 45 — for  live  load  strains, 

bridges.  r 

P=2o ,000 — 90 — for  dead  load  strains. 

r 


All  posts  of  1 

deck  bridges  ^=11,000 — 40 — for  live  load  strains, 
and  trestles.  r 

P=2 2,000 — 80— for  dead  load  strains. 

r 


End  posts  are  not  to  be  considered  chord  segments. 

Lateral  struts  j 

and  rigid  P=  13, 000 — 60 — for  wind  strains; 
bracing.  r 

for  live  load  strains  use  two-thirds  of  the  above.  (§§  42,  43, 
124.)  ____  _  . . 

P=the  allowed  strain  in  compression  per  square  inch  of 
cross-section,  in  pounds. 

/=the  length  of  compression  member,  in  inches,  c.  to  c., 
of  connections. 

r=the  least  radius  of  gyration  of  the  section,  in  inches. 
No  compression  member,  however,  shall  have  a  length 


12 


exceeding  ioo  times  its  least  radius  of  gyration  for  main 
members,  or  120  times  for  laterals. 

For  swing  bridges  and  other  movable  structures,  the 
dead  load  unit  strains  during  motion  must  not  exceed  £  of 
the  above  allowed  unit  strains  for  dead  load  on  stationary 
structures. 

49.  For  long  span  bridges,  when  the  ratio  of  the  length 
and  width  of  span  is  such  that  it  makes  the  top  chords  acting 
as  a  whole,  a  longer  column  than  the  segments  of  the  chord, 
the  chord  will  be  proportioned  for  this  greater  length. 

soft  steei.  Soft  Steel  may  be  used  in  compression  with  unit  strains 
fifteen  per  cent,  less  than  those  allowed  for  Medium  Steel. 

50.  The  areas  obtained  by  dividing  the  live  load  strains  by 
the  live  load  unit  strains  will  be  added  algebraically  to  the 
areas  obtained  by  dividing  the  dead  load  strains  by  the 
dead  load  unit  strains  to  determine  the  required  sectional 
area  of  any  member.  (§  62.) 

Alternate  51.  All  members  and  their  connections  subject  to  alter- 
nate  strains  01  tension  and  compression  shall  be  propor¬ 
tioned  to  resist  each  kind  of  strain.  Both  of  the  strains  shall, 
however,  be  considered  as  increased  by  an  amount  equal  to 
t8o  of  the  least  of  the  two  strains,  for  determining  the  sec¬ 
tional  areas  by  the  above-allowed  unit  strains.  (§§45,48.) 

Effect  of  wind  5 2 .  The  strains  in  the  truss  members  or  trestle  posts 

on  Chord  ,  .  .  ^ 

strains.  from  the  assumed  wind  forces  need  not  be  considered  ex¬ 

cept  as  follows : 

ist.  When  the  wind  strains  on  any  member  exceed  25 
per  cent,  of  the  maximum  strains  due  to  the  dead  and  live 
loads  upon  the  same  member.  The  section  shall  then  be 
increased  until  the  total  strain  per  square  inch  will  not 
exceed  by  more  than  25  per  cent,  the  maximum  fixed  for 
dead  and  live  loads  only. 

2d.  When  the  wind  strain  alone  or  in  combination  with  a 
possible  temperature  strain,  can  neutralize  or  reverse  the 
strains  in  any  member. 

Rivets,  Bolts  53.  The  rivets  in  all  members,  other  than  those  of  the 

and  Pins.  n 

floor  and  lateral  systems,  must  be  so  spaced  that  the  shear¬ 
ing  strain  per  square  inch  shall  not  exceed  10,000  pounds; 


13 


nor  the  pressure  on  the  bearing  surface  (diameter  X  thick¬ 
ness  of  the  piece)  of  the  rivet-hole  exceed  18,000  pounds 
per  square  inch. 

The  rivets  in  all  members  of  the  floor  system,  including 
all  hanger  connections,  must  be  so  spaced  that  the  shearing 
strains  and  bearing  pressures  shall  not  exceed  80  per  cent, 
of  the  above  limits. 

The  rivets  in  the  lateral  and  sway  bracing  will  be  allowed 
40  per  cent,  increase  upon  the  above  limits. 

In  the  case  of  field  riveting  (and  for  bolts  as  per  §  76)  the 
above-allowed  shearing  strains  and  pressures  shall  be  re¬ 
duced  one-third. 

Rivets  and  bolts  must  not  be  used  in  direct  tension. 

54.  Pins  shall  be  proportioned  so  that  the  shearing  strain 
shall  not  exceed  10,000  pounds  per  square  inch  ;  nor  the 
pressure  on  the  bearing  surface  of  any  member  (other  than 
forged  eye-bars,  see  §  104)  connected  to  the  pin  be  greater 
per  square  inch  than  18,000  pounds  ;  nor  the  bending  strain 
exceed  20,000  pounds,  when  the  applied  forces  are  consid¬ 
ered  as  uniformly  distributed  over  the  middle  half  of  the 
bearing  of  each  member. 

55.  When  any  member  is  subjected  to  the  action  of  both  combined 
axial  and  bending  strains,  as  in  the  case  of  end  posts  0fstra,ns' 
through  bridges  (§  52),  or  of  chords  carrying  distributed 
floor  loads,  it  must  be  proportioned  so  that  the  greatest 
fibre  strain  will  not  exceed  the  allowed  limits  of  tension  or 
compression  on  that  member. 

If  the  fibre  strain  resulting  from  the  weight  only,  of  any 
member,  exceeds  ten  per  cent,  of  the  allowed  unit  strain  on 
such  member,  such  excess  must  be  considered  in  propor¬ 
tioning  the  areas. 

56.  In  beams  and  plate  girders  the  compression  flanges  Compression 
shall  be  made  of  same  section  as  the  tension  flanges. 

57.  Riveted  longitudinal  girders  shall  have,  preferably,  a  Depth  of 
depth  not  less  than  ^  of  the  span. 

Rolled  beams  used  as  longitudinal  girders  shall  have, 
preferably,  a  depth  not  less  than  of  the  span. 

58.  Plate  girders  shall  be  proportioned  upon  the  supposi-  Plate  Girders 


14 


tion  that  the  bending  or  chord  strains  are  resisted  entirely 
by  the  upper  and  lower  flanges,  and  that  the  shearing  or 
web  strains  are  resisted  entirely  by  the  web-plate  ;  no  part 
of  the  web-plate  shall  be  estimated  as  flange  area. 

The  distance  between  centres  of  gravity  of  the  flange 
areas  will  be  considered  as  the  effective  depth  of  all  girders, 
web  piates.  59.  The  webs  of  plate  girders  must  be  stiffened  at  inter¬ 
vals,  not  exceeding  the  depth  of  the  girders  or  a  maximum 
of  5  feet,  wherever  the  shearing  strain  per  square  inch  ex¬ 
ceeds  the  strain  allowed  by  the  following  formula  : 

Allowed  shearing  strain  =  12,500  —  9 oH, 

where  H  =  ratio  of  depth  of  web  to  its  thickness  ;  but  no 
web-plates  shall  be  less  than  t5q  of  an  inch  in  thickness. 

Stiffeners.  60.  All  stiffeners  must  be  capable  of  carrying  the  maximum 
vertical  shear  without  exceeding  the  allowed  unit  strain. 

P=  12,000  —  55-. 

r 

Each  stiffener  must  connect  to  the  webs  by  enough  rivets 
to  transfer  the  maximum  shear  to  or  from  the  webs  (§  83). 

Rolled  Beams.  61.  Rolled  beams  shall  be  proportioned  (§§  45,  48)  by 
their  moments  of  inertia. 

Counters.  62.  The  areas  of  counters  shall  be  determined  by  taking 
the  difference  in  areas  due  to  the  live  and  dead  load  strains 
considered  separately  (§  45,  105). 

63.  For  bridges  carrying  electric  or  motor  cars  counters 
shall  be  provided  and  proportioned,  so  that  a  future  increase 
of  25  per  cent,  in  the  specified  live  load  shall  notin  any  case 
increase  the  allowed  unit  strain  more  than  25  per  cent. 

DETAILS  OF  CONSTRUCTION. 

Details.  64.  All  the  connections  and  details  of  the  several  parts  of 
the  structures  shall  be  of  such  strength  that,  upon  testing, 
rupture  will  occur  in  the  body  of  the  members  rather 
than  in  any  of  their  details  or  connections. 

65.  Preference  will  be  had  for  such  details  as  shall  be 
most  accessible  for  inspection,  cleaning  and  painting  ;  no 
closed  sections  will  be  allowed. 

Riveting.  66.  The  pitch  of  rivets  in  all  classes  of  work  shall  never 


* 


15 


exceed  6  inches,  or  sixteen  times  the  thinnest  outside  plate, 
nor  be  less  than  three  diameters  of  the  rivet. 

67.  The  rivets  used  shall  generally  be  f  and  |  inch  diameter. 

68.  The  distance  between  the  edge  of  any  piece  and  the 
centre  of  a  rivet-hole  must  never  be  less  than  iy  inches, 
except  for  bars  less  than  2-§  inches  wide  ;  when  practicable 
it  shall  be  at  least  two  diameters  of  the  rivet. 

69.  For  punching,  the  diameter  of  the  die  shall  in  no  case 
exceed  the  diameter  of  the  punch  by  more  than  of  an 
inch,  and  all  holes  must  be  clean  cuts  without  torn  or 
ragged  edges. 

70.  All  rivet  holes  must  be  so  accurately  spaced  and 
punched  that  when  the  several  parts  forming  one  member 
are  assembled  together,  a  rivet  y1^  inch  less  in  diameter  than 
the  hole  can  generally  be  entered,  hot,  into  any  hole,  with¬ 
out  reaming  or  straining  the  metal  by  “  drifts  occasional 
variations  must  be  corrected  by  reaming. 

71.  The  rivets  when  driven  must  completely  fill  the 
holes.  The  rivet-heads  must  be  round  and  of  a  uniform  size 
for  the  same  sized  rivets  throughout  the  work.  They  must 
be  full  and  neatly  made,  and  be  concentric  to  the  rivet-hole, 
and  thoroughly  pinch  the  connected  pieces  together. 

72.  Wherever  possible,  all  rivets  must  be  machine  driven. 

The  machines  must  be  capable  of  retaining  the  applied 
pressure  after  the  upsetting  is  completed.  No  hand-driven 
rivets  exceeding  $  inch  diameter  will  be  allowed. 

73.  Field  riveting  must  be  reduced  to  a  minimum  or 
entirely  avoided,  where  possible. 

74.  All  holes  for  field  rivets,  except  those  in  connections 
of  the  lateral  and  sway  systems,  shall  be  accurately  drilled 
or  reamed  to  an  iron  template  or  be  reamed  true  while  the 
parts  are  temporarily  connected  together. 

75.  The  effective  diameter  of  a  driven  rivet  will  be  as-  Net  Sections, 
sumed  the  same  as  its  diameter  before  driving.  In  deduct¬ 
ing  the  rivet-holes  to  obtain  net  sections  in  tension  mem¬ 
bers,  the  diameter  of  the  rivet-holes  will  be  assumed  as  •§■ 

inch  larger  than  the  undriven  rivets. 

The  rupture  of  a  riveted  tension  member  is  to  be  con- 


16 


Bolts. 


Splices. 


Abutting  Joints. 


Web  Splices. 


Stiffeners. 


sidered  as  equally  probable,  either  through  a  transverse 
line  of  rivet-holes  or  through  a  diagonal  line  of  rivet-holes, 
where  the  net  section  does  not  exceed  by  30  per  cent,  the 
net  section  along  the  transverse  line. 

The  number  of  rivet-holes  to  be  deducted  for  net  section 
will  be  determined  by  this  condition.  (§§  47-79.) 

76.  When  members  are  connected  by  bolts  the  holes  must 
be  reamed  parallel  and  the  bolts  turned  to  a  driving  fit. 
All  bolts  must  be  of  neat  lengths,  and  shall  have  a  washer 
under  the  heads  and  nuts  where  in  contact  with  wood. 
Bolts  must  not  be  used  in  place  of  rivets,  except  by  special 
permission. 

77.  All  nuts  must  be  of  hexagonal  shape. 

78.  All  joints  in  riveted  tension  members  must  be  fully 
and  symmetrically  spliced. 

79.  Riveted  tension  members  shall  have  an  effective  sec¬ 
tion  through  the  pin-holes  25  per  cent,  in  excess  of  the  net 
section  of  the  member,  and  back  of  the  pin  at  least  75 
per  cent,  of  the  net  section  through  the  pin-hole. 

80.  In  continuous  compression  members,  as  chords  and 
trestle  posts,  the  abutting  joints  with  planed  laces  must  be 
placed  as  close  to  the  panel  points  as  is  practicable,  and  the 
joints  must  be  spliced  on  all  sides  with  at  least  two  rows  of 
closely  pitched  rivets  on  each  side  of  the  joint. 

Joints  in  long  posts  must  be  fully  spliced. 

81.  In  compression  members,  abutting  joints  with  un¬ 
tooled  faces  must  be  fully  spliced,  as  no  reliance  will  be 
placed  on  such  abutting  joints.  The  abutting  ends  must, 
however,  be  dressed  straight  and  true,  so  there  will  be  no 
open  joints. 

82.  The  webs  of  plate  girders  must  be  spliced  at  all  joints 
by  a  plate  on  each  side  of  the  web. 

83.  All  web-plates  must  have  stiffeners  over  bearing 
points  and  at  points  of  local  concentrated  loadings ;  such 
stiffeners  must  be  fitted  at  their  ends  to  the  flange  angles, 
at  the  bearing  points.  (§§  59-60.) 

84.  All  other  angles,  filling  and  splice  plates  on  the  webs 
of  girders  and  riveted  members  must  fit  at  their  ends  to 


17 


the  flange  angles,  sufficiently  close  to  be  sealed,  when 
painted,  against  admission  of  water. 

85.  Web-plates  of  all  girders  must  be  arranged  so  as  not  web  Plates, 
to  project  beyond  the  faces  of  the  flange  angles,  nor  on  the 

top  be  more  than  T^-  inch  below  the  face  of  these  angles,  at 
any  point. 

86.  Wherever  there  is  a  tendency  for  water  to  collect, 
the  spaces  must  be  filled  with  a  suitable  waterproof  material. 

87.  In  girders  with  flange  plates,  at  least  one-half  of  the  Flange  Plates, 
flange  section  shall  be  angles  or  else  the  largest  sized  angles 

must  be  used.  Flange  plates  must  extend  beyond  their 
theoretical  length,  two  rows  of  rivets  at  each  end. 

88.  The  flange  plates  of  all  girders  must  be  limited  in 
width  so  as  not  to  extend  beyond  the  outer  lines  of  rivets 
connecting  them  with  the  angles,  more  than  five  inches  or 
more  than  eight  times  the  thickness  of  the  first  plate.  Where 
two  or  more  plates  are  used  on  the  flanges,  they  shall  either 
be  of  equal  thickness  or  shall  decrease  in  thickness  outward 
from  the  angles. 

89.  The  compression  flanges  of  beams  and  girders  shall  be  Compression 
stayed  against  transverse  crippling  when  their  length  is 

more  than  sixteen  times  their  width. 

90.  The  unsupported  width  (distance  between  rivets)  of  width  oi  plates, 
plates  subject  to  compression  shall  not  exceed  thirty  times 

their  thickness ;  except  cover  plates  of  top  chords  and  end 
posts,  which  will  preferably  be  limited  to  forty  times  their 
thickness  ;  where  a  greater  relative  width  is  used  in  chords 
and  end  posts,  however,  only  forty  times  the  thickness 
shall  be  considered  as  effective  section. 

91.  In  lattice  girders  and  trusses  the  web  members  must 
be  double  and  connect  symmetrically  to  the  webs  of  the 
chords.  The  use  of  plates  or  flats,  alone,  for  tension  mem¬ 
bers  must  be  avoided,  where  it  is  possible ;  in  lattice 
trusses,  the  counters,  suspenders  and  two  panels  of  the 
lower  chord,  at  each  end,  must  be  latticed ;  all  other  ten¬ 
sion  members  must  be  connected  by  batten  plates  or  latticed. 

(§  hi.) 

92.  Where  the  floor  timbers  are  supported  at  their  ends 


18 


on  the  flange  of  one  angle,  such  angle  must  have  two  rows 
ol  rivets  in  its  vertical  leg,  spaced  not  over  4  inches  apart. 

Buckie  Plates.  93.  Buckle  plates  must  be  firmly  riveted  to  the  support¬ 
ing  beams  and  be  spliced  at  all  free  edges.  Preferably 
they  will  be  made  in  continuous  sheets  of  panel  lengths. 
They  may  be  pressed  or  formed  without  heating.  (§  23.) 

94.  A  buckle-plate  floor,  as  specified,  may  be  considered 
as  the  required  lateral  system  of  bracing  at  the  floor  level. 

95.  The  buckle-plates  of  the  sidewalks  will  be  covered  to 
the  proper  slope  and  level  for  the  wearing  pavement  with 
bitumen  concrete  of  an  accepted  and  waterproof  character. 

96.  The  buckle-plates  of  the  roadway  will  be  covered 
with  an  acceptable  and  waterproof  concrete  (bitumen  or 
cement)  to  the  proper  crown  and  grade  for  the  wearing 
pavement,  but  at  no  place  must  the  concrete  be  less  than  3 
inches  thick. 

Thickness  of  9 7-  For  main  members  and  their  connections  no  material 
shall  be  used  of  a  less  thickness  than  T5^  of  an  inch  ;  and  for 
laterals  and  their  connections,  no  material  less  than  J  of 
an  inch  in  thickness  ;  except  for  lining  or  filling  vacant 
spaces.  No  bars  shall  be  used  with  a  less  net  area  than  f 
of  one  square  inch. 

Eye  Bars  98.  The  heads  of  eye-bars  shall  be  so  proportioned  and 
made,  that  the  bars  will  preferably  break  in  the  body  of 
the  original  bar  rather  than  at  any  part  of  the  head  or  neck. 
The  form  of  the  head  and  the  mode  of  manufacture  shall  be 
subject  to  the  approval  of  the  Engineer.  (§§  138,  139,  159, 
160.) 

99.  The  bars  must  be  free  from  flaws  and  of  full  thick¬ 
ness  in  the  necks.  They  shall  be  perfectly  straight  before 
boring.  The  holes  shall  be  in  the  centre  of  the  head,  and 
on  the  centre  line  of  the  bar. 

100.  The  bars  must  be  bored  to  lengths  not  varying  from 
the  calculated  lengths  more  than  -g1^  of  an  inch  for  each  25 
feet  of  total  length. 

101.  Bars  which  are  to  be  placed  side  by  side  in  the 
structure  shall  be  bored  at  the  same  temperature  and  of 
such  equal  length  that  upon  being  piled  on  each  other  the 


19 


pins  shall  pass  through  the  holes  at  both  ends  without 
driving. 

102.  The  lower  chord  shall  be  packed  as  narrow  as  possi¬ 
ble. 

103.  The  pins  shall  be  turned  straight  and  smooth;  chord  p;ns. 
pins  shall  fit  the  pin-holes  within  ^  of  an  inch,  for  pins  less 
than  4-J  inches  diameter;  for  pins  of  a  larger  diameter  the 
clearance  may  be  inch. 

104.  The  diameter  of  the  pin  shall  not  be  less  than  three- 
quarters  the  largest  dimension  of  any  eye-bar  attached  to  it. 

The  several  members  attaching  to  the  pin  shall  be  so 
packed  as  to  produce  the  least  bending  moment  upon  the 
pin,  and  all  vacant  spaces  must  be  filled  with  wrought  fill¬ 
ing  rings. 

105.  All  bars  with  screw  ends  shall  be  upset  at  the  ends,  Upset  Ends, 
so  that  the  diameter  at  the  bottom  of  the  threads  shall  be 

-Jg-  inch  larger  than  any  part  of  the  body  of  the  bar.  Where 
closed  sleeve  nuts  are  used  on  adjustable  members  the 
effective  length  of  thread  shall  be  legibly  stamped  at  the 
screw  ends  of  each  bar.  Adjustable  counters  to  be  avoided 
where  practicable. 

106.  All  threads  must  be  of  the  United  States  standard, 
except  at  the  ends  of  the  pins. 

107.  Floor  beam  hangers  when  permitted  shall  be  made  Hangers, 
without  adjustment  and  so  placed  that  they  can  be  readily 
examined  at  all  times.  (§  3.) 

108.  All  the  floor  beams  must  be  effectually  stayed  against 
end  motion  or  any  tendency  to  rotate  from  the  action  of  the 
lateral  system. 

ioq.  Compression  members  shall  be  of  steel,  and  of  ap-  Compression 

Members. 

proved  forms. 

no.  The  pitch  of  rivets  at  the  ends  of  compression  mem¬ 
bers  shall  not  exceed  four  diameters  of  the  rivets  for  a 
length  equal  to  twice  the  width  of  the  member. 

hi.  The  open  sides  of  all  compression  members  shall  be 
stayed  by  batten  plates  at  the  ends  and  diagonal  lattice- 
work  at  intermediate  points.  The  batten  plates  must  be 
placed  as  near  the  ends  as  practicable,  and  shall  have  a 


20 


length  not  less  than  the  greatest  width  of  the  member  or  i \ 
times  its  least  width.  The  size  and  spacing  of  the  lattice 
bars  shall  be  duly  proportioned  to  the  size  of  the  member. 
They  must  not  be  less  in  width  than  i-J  inches  for  mem¬ 
bers  6  inches  jin  width,  if  inches  for  members  9  inches  in 
width,  2  inches  for  members  12  inches  in  width,  nor  21- 
inches  for  members  15  inches  in  width,  nor  2\  inches  for 
members  18  inches  and  over  in  width.  Single  lattice  bars 
shall  have  a  thickness  not  less  than  ^  or  double  lattice  bars 
connected  by  a  rivet  at  the  intersection,  not  less  than  of 
the  distance  between  the  rivets  connecting  them  to  the 
members.  They  shall  be  inclined  at  an  angle  not  less  than 
6o°  to  the  axis  of  the  member  for  single  latticing,  nor  less 
than  450  for  double  latticing  with  riveted  intersections. 
The  pitch  of  the  latticing  must  not  exceed  the  width  of  the 
channel  plus  nine  inches. 

1 12.  Where  necessary,  pin-holes  shall  be  reinforced  by 
plates,  some  of  which  must  be  of  the  full  width  of  the 
member,  so  the  allowed  pressure  on  the  pins  shall  not  be 
exceeded,  and  so  the  strains  shall  be  properly  distributed 
over  the  full  cross-section  of  the  members.  These  reinforc¬ 
ing  plates  must  contain  enough  rivets  to  transfer  their  pro¬ 
portion  of  the  bearing  pressure,  and  at  least  one  plate  on 
each  side  shall  extend  not  less  than  six  inches  beyond  the 
edge  of  the  batten  plates.  (§  111.) 

1 13.  Where  the  ends  of  compression  members  are  forked 
to  connect  to  the  pins,  the  aggregate  compressive  strength 
of  these  forked  ends  must  equal  the  compressive  strength 
of  the  body  of  the  members. 

1 14.  In  compression  chord  sections  and  end  posts,  the 

material  must  mostly  be  concentrated  at  the  sides,  in  the 
angles  and  vertical  webs.  Not  more  than  one  plate,  and 
this  not  exceeding  §  inch  in  thickness,  shall  be  used  as  a 
cover  plate,  except  when  necessary  to  resist  bending  strains, 
or  to  comply  with  §  90.  (§55.) 

1 15.  The  ends  of  all  square-ended  members  shall  be 
planed  smooth,  and  exactly  square  to  the  centre  line  of 
strain. 


21 


1 1 6.  The  ends  of  all  floor  beams  and  stringers  shall  be  Floor  Beams 
faced  true  and  square,  and  to  correct  lengths.  Allowance and  Strmgers 
must  be  made  in  the  thickness  of  the  end  angles  to  provide 

for  such  facing  without  reducing  the  required  effective 
strength  of  such  end  angles. 

11 7.  All  members  must  be  free  from  twists  or  bends.  Por¬ 
tions  exposed  to  view  shall  be  neatly  finished. 

1 18.  Pin-holes  shall  be  bored  exactly  perpendicular  to  aPin-Hoies. 
vertical  plane  passing  through  the  centre  line  of  each  mem¬ 
ber,  when  placed  in  a  position  similar  to  that  it  is  to  occupy 

in  the  finished  structure. 

1 19.  The  several  pieces  forming  one  built  member  must 
fit  closely  together,  and  when  riveted  shall  be  free  from 
twists,  bends  or  open  joints. 

120.  All  through  bridges  shall  have  latticed  portals,  of  Transverse 
approved  design,  at  each  end  of  the  span,  connected  rigidly  Bracing 
to  the  end  posts  and  top  chords.  They  shall  be  as  deep  as 

the  specified  head-room  will  allow,  and  provision  shall  be 
made  in  the  end  posts  for  the  bending  strains  from  wind 
pressure.  (§§  4,  10,  39,  52.) 

121.  When  the  height  of  the  trusses  exceeds  20  feet,  an 
approved  system  of  overhead  diagonal  bracings  shall  be 
attached  to  each  post  and  to  the  top  lateral  struts. 

122.  Knee  braces  shall  be  placed  at  each  intermediate 
panel  point,  and  connected  to  the  vertical  posts  and  top 
lateral  struts,  for  trusses  20  feet  and  less  in  depth. 

123.  Pony  trusses  and  through  plate  or  lattice  girders 
shall  be  stayed  by  knee  braces  or  gusset  plates  attached  to 
the  top  chords  at  the  ends  and  at  intermediate  points,  and 
attached  below  to  the  cross  floor  beams  or  to  the  transverse 
struts. 

124.  All  deck  girders  shall  have  transverse  braces  at  the 
ends.  All  deck  bridges  shall  have  transverse  bracing  at 
each  panel  point.  This  bracing  shall  be  proportioned  to 
resist  the  unequal  loading  of  the  trusses. 

12$.  All  members  of  the  web,  lateral,  longitudinal  or  sway 
systems  must  be  securely  riveted  at  their  intersections  to 
prevent  sagging  and  rattling. 


22 


Bed  Plates.  12 6.  All  bed-plates  must  be  of  such  dimensions  that  the 
greatest  pressure  upon  the  pedestal  stone  shall  not  exceed 
250  pounds  per  square  inch. 

Friction  127 .  All  bridges  over  8o  feet  span  shall  have  hinged 
RoUers. bolsters  on  both  ends,  and  at  one  end  nests  of  turned  fric¬ 
tion  rollers  running  between  planed  surfaces.  These  rollers 
shall  not  be  less  than  2-J  inches  diameter  for  spans  ioo  feet 
or  less,  and  for  greater  spans  this  diameter  shall  be  increased 
in  proportion  of  i  inch  for  ioo  feet  additional. 

The  rollers  shall  be  so  proportioned  that  the  pressure 
per  lineal  inch  of  roller  shall  not  exceed  the  product  of  the 
diameter  in  inches  by  300  pounds  (30od.). 

The  rollers  must  be  of  machinery  steel  and  the  bearing 
plates  of  medium  steel. 

The  rollers  and  bearings  must  be  so  arranged  that  they 
can  be  readily  cleaned  and  so  that  they  will  not  hold  water. 

128.  Bridges  less  than  80  feet  span  shall  be  secured  at 
one  end  to  the  masonry,  and  the  other  end  shall  be  free  to 
move  longitudinally  upon  smooth  surfaces. 

129.  Where  two  spans  rest  upon  the  same  masonry,  a  con¬ 
tinuous  plate,  not  less  than  f  inch  thick,  shall  extend  under 
the  two  adjacent  bearings,  or  the  two  bearings  must  be 
rigidly  tied  together. 

Pedestals  and  1 30.  Pedestals  shall  be  made  of  riveted  plates  and  angles. 

Bed-Plates.  •  • 

All  bearing  surfaces  of  the  base  plates  and  vertical  webs 
must  be  planed.  The  vertical  webs  must  be  secured  to  the 
base  by  angles  having  two  rows  of  rivets  in  the  vertical 
legs.  No  base  plate  or  web  connecting  angle  shall  be  less 
in  thickness  than  \  inch.  The  vertical  webs  shall  be  of 
sufficient  height  and  must  contain  material  and  rivets 
enough  to  practically  distribute  the  loads  over  the  bearings 
or  rollers. 

Where  the  size  of  the  pedestal  permits,  the  vertical  webs 
must  be  rigidly  connected  transversely. 

1 3 1 .  All  the  bed-plates  and  bearings  under  fixed  and 
movable  ends  must  be  fox-bolted  to  the  masonry ;  for 
trusses,  these  bolts  must  not  be  less  than  inches  diameter ; 
for  plate  and  other  girders,  not  less  than  |  inch  diameter. 


23 


The  contractor  must  furnish  all  bolts,  drill  all  holes  and  set 
bolts  to  place  with  sulphur  or  Portland  cement. 

132.  While  the  expansion  ends  of  all  trusses  must  be  free 
to  move  longitudinally  under  changes  of  temperature,  they 
shall  be  anchored  against  lifting  or  moving  sideways. 

133.  All  bridges  shall  be  cambered  by  giving  the  panels  Camber, 
of  the  top  chord  an  excess  of  length  in  the  proportion  of 

of  an  inch  to  every  ten  feet. 

134.  The  lower  struts  in  trestle  towers  must  be  capable  Trestle  Towers, 
of  resisting  the  strains  due  to  changes  of  temperature  or  of 
moving  the  tower  pedestals  under  the  effects  of  expansion 

or  contraction. 

For  high  or  massive  towers,  these  lower  struts  will  be 
securely  anchored  to  intermediate  masonry  piers,  or  the 
tower  pedestals  will  have  suitably  placed  friction  rollers, 
as  may  be  directed  by  the  Engineer. 

135.  All  joints  in  the  tower  columns  shall  be  fully  spliced 
for  all  possible  tension  strains,  and  to  hold  the  parts  firmly 
in  position.  (§  80.) 

136.  Tower  footings  and  bed-plates  must  be  planed  on 
all  bearing  surfaces;  and  the  holes  for  anchor  bolts  slotted 
to  allow  for  the  proper  amount  of  movement.  (§  41.) 

137.  All  workmanship  shall  be  first-class  in  every  par-  Workmanship, 
ticular. 

138.  All  eye-bars  must  be  made  of  medium  steel.  Eye-Bars. 

139.  Eye-bars,  all  forgings  and  any  pieces  which  have 
been  partially  heated  or  bent  cold  must  be  wholly  an¬ 
nealed.  Crimped  stiffeners  need  not  be  annealed. 

140.  No  reliance  will  be  placed  upon  the  welding  of 
steel. 

141.  No  sharp  or  unfilleted  angles  or  corners  will  be 
allowed  in  any  piece  of  metal. 

142.  Medium  steel  maybe  used  in  compression  in  chords,  Medium  steel, 
posts  and  pedestals  without  reaming  of  punched  holes,  for 

all  thicknesses  of  metal,  which  will  stand  the  drifting  test 
§  154);  provided  all  sheared  edges  are  planed  off  to  a  depth 
of  -J  inch. 

In  all  other  cases  medium  steel  over  f  inch  thick  must 


24 


Soft  Steel, 


Pilot  Nuts 


have  all  sheared  edges  planed  off  to  a  depth  of  |  inch  and 
all  holes  drilled  or  reamed  to  a  diameter  £  inch  larger  than 
the  punched  holes,  so  as  to  remove  all  the  sheared  surface 
of  the  metal. 

143.  Soft  steel  need  not  be  reamed  if  it  satisfies  the  drift- 
ing  test  (§§  154,  155). 

144.  All  parts  of  any  tension  or  compression  flange  or 
member,  must  be  of  the  same  kind  of  steel,  but  webs  of 
plate  girders  and  the  tension  members  of  all  girders,  plate 
or  lattice,  may  be  made  of  soft  steel  in  connection  with 
compression  members  of  medium  steel. 

145.  All  splices  must  be  of  the  same  kind  of  steel  as  the 
parts  to  be  joined. 

146.  Pilot  nuts  must  be  used  during  the  erection  to  pro¬ 
tect  the  threads  of  the  pins.  * 


QUALITY  OF  MATERIAL. 

Steel. 

147.  All  steel  must  be  made  by  the  Open  Hearth  process. 
The  phosphorus  must  not  exceed  0.06  of  one  per  cent,  for 
steel  made  by  the  acid  method,  or  0.04  for  steel  by  the  basic 
method. 

148.  The  steel  must  be  uniform  in  character  for  each 
specified  kind.  The  finished  bars,  plates  and  shapes  must 
be  free  from  cracks  on  the  faces  or  corners,  and  have  a 
clean,  smooth  finish.  No  work  shall  be  put  upon  any  steel 
at  or  near  the  blue  temperature  or  between  that  of  boiling 
water  and  of  ignition  of  hard  wood  sawdust. 

149.  The  tensile  strength,  elastic  limit*  and  ductility  shall 
be  determined  by  samples  cut  from  the  finished  material 
after  rolling.  The  samples  to  be  at  least  12  inches  long, 
and  to  have  a  uniform  sectional  area  not  less  than  J  square 
inch. 


*  For  the  purpose  of  these  specifications,  the  Elastic  Limit  will  be  considered  the  least 
strain  producing  a  visible  permanent  elongation  in  a  length  of  8  inches,  as  shown  by  scribe 
marks  of  a  pair  of  finely  pointed  dividers. 

If  the  yield  point  or  drop  of  the  beam  can  be  calibrated  for  any  machine  and  its  speed  to 
represent  the  elastic  limit  within  5  percent.,  it  may  be  used  for  general  cases.  Test  reports 
must  state  by  which  method  the  elastic  limit  was  determined. 


25 


150.  Material  which  is  to  be  used  without  annealing  or 
further  treatment  is  to  be  tested  in  the  condition  in  which 
it  comes  from  the  rolls.  When  material  is  to  be  annealed 
or  otherwise  treated  before  use,  the  specimen  representing 
such  material  is  to  be  similarly  treated  before  testing,  for 
tensile  strength. 

The  elongation  shall  be  measured  on  an  original  length  of 
8  inches.  Two  test  pieces  shall  be  taken  from  each  melt  or 
blow  of  finished  material,  one  for  tension  and  one  for  bend¬ 
ing.  (Art.  166.) 

1 5 1.  All  samples  or  full-sized  pieces  must  show  uniform 
fine  grained  fractures  of  a  blue  steel-gray  color,  entirely 
free  from  fiery  lustre  or  a  blackish  cast. 

152.  Medium  Steel  shall  have  an  ultimate  strength,  when  Medium  Steel, 
tested  in  samples  of  the  dimensions  above  stated,  of  60,000 

to  68,000  pounds  per  square  inch,  an  elastic  limit  of  not 
less  than  one-half  of  the  ultimate  strength,  and  a  minimum 
elongation  of  22  per  cent,  in  8  inches.  Steel  for  pins  may 
have  a  minimum  elongation  of  15  per  cent. 

153.  Before  or  after  heating  to  a  low  cherry  red  and 
cooling  in  water  at  82  degrees  Fahr.,  this  steel  must  stand 
bending  to  a  curve  whose  inner  radius  is  one  and  a  half 
times  the  thickness  of  the  sample,  without  cracking. 

154.  For  all  medium  steel,  §  inch  or  less  in  thickness, 
rivet  holes  punched  as  in  ordinary  practice  (§§  68,  69,  70), 
must  stand  drifting  to  a  diameter  one-third  greater  than 
the  original  holes,  without  cracking  either  in  the  periphery 
of  the  holes  or  on  the  external  edges  of  the  piece,  whether 
they  be  sheared  or  rolled. 

155.  Soft  Steel  Shall  have  an  ultimate  strength,  on  same  soft  steel, 
sized  samples,  of  54,000  to  62,000  pounds  per  square 
inch,  an  elastic  limit  not  less  than  one-half  the  ultimate 
strength,  and  a  minimum  elongation  of  25  per  cent,  in  8 
inches. 

For  soft  steel  the  above  drifting  test  (§  154)  shall  apply  to 
all  material  to  be  riveted. 

156.  Before  or  after  heating  to  a  light  yellow  heat  and 
quenching  in  cold  water,  this  steel  must  stand  bending  180 


«s 


26 


Rivet  Steel. 


Eye  Bars, 


Pins. 


Steel  Castings. 


degrees,  to  a  curve  whose  inner  radius  is  equal  to  the 
thickness  of  the  sample,  without  sign  of  fracture. 

157.  Rivet  Steel  shall  have  an  ultimate  strength  of  50,000 
to  58,000  pounds  per  square  inch,  an  elastic  limit  not  less 
than  one-half  the  ultimate  strength  and  an  elongation  of  26 
per  cent. 

158.  The  steel  for  rivets  must,  under  the  above  bending 
test  (156),  stand  closing  solidly  together  without  sign  of 
fracture. 

159.  Eye-bar  material,  ij  inches  and  less  in  thickness, 
shall,  on  test  pieces  cut  from  finished  material,  fill  the  above 
requirements.  For  thicknesses  greater  than  i-J  inches,  there 
will  be  allowed  a  reduction  in  the  percentage  of  elongation 
of  1  per  cent,  for  each  -§■  of  an  inch  increase  of  thickness,  to 
a  minimum  of  20  per  cent.  (Art.  138.) 

160.  Full  sized  eye-bars  shall  show  not  less  than  10  per 
cent,  elongation  in  the  body  of  the  bar,  and  an  ultimate 
strength  not  less  than  56,000  pounds  per  square  inch. 
Should  a  bar  break  in  the  head,  but  develop  10  per  cent, 
elongation  and  the  ultimate  strength  specified,  it  shall  not 
be  cause  for  rejection,  provided  not  more  than  one-third  of 
the  total  number  of  bars  tested  break  in  the  head. 

1 6 1 .  Pins  over  7  inches  in  diameter  shall  be  forged. 
Blooms  for  pins  shall  have  at  least  three  times  the  sectional 
area  of  the  finished  pins. 

162.  A  variation  of  cross-section  or  weight  in  the  finished 
members  of  2-J-  per  cent,  from  the  specified  size  may  be 
cause  for  rejection. 


Steel  Castings. 

163.  Steel  castings  will  be  used  for  drawbridge  wheels, 
track  segments  and  gearing.  (Art.  1.) 

They  must  be  true  to  form  and  dimensions,  of  a  work¬ 
manlike  finish  and  free  from  injurious  blowholes  and 
defects.  All  castings  must  be  annealed. 

When  tested  in  specimens  of  uniform  sectional  area  of  at 
least  -J  square  inch  for  a  distance  of  2  inches,  they  must 


27 


show  an  ultimate  strength  of  not  less  than  67,000  pounds 
per  square  inch,  an  elastic  limit  of  one-half  the  ultimate, 
and  an  elongation  in  2  inches  of  not  less  than  10  per  cent. 

The  metal  must  be  uniform  in  character,  free  from  hard 
or  soft  spots,  and  be  capable  of  being  properly  tool  finished. 

Cast  Iron. 

164.  Except  where  cast  steel  or  chilled  iron  is  required,  Cast  Iron, 
all  castings  must  be  of  tough,  gray  iron,  free  from  cold 
shuts  or  injurious  blowholes,  true  to  form  and  thickness, 

and  of  a  workmanlike  finish.  Sample  pieces,  1  inch  square, 
cast  from  the  same  heat  of  metal  in  sand  moulds,  shall  be 
capable  of  sustaining,  on  a  clear  span  of  12  inches,  a  central 
load  of  2,400  pounds,  when  tested  in  the  rough  bar.  A  blow 
from  a  hammer  shall  produce  an  indentation  on  a  rectangu¬ 
lar  edge  of  the  casting  without  flaking  the  metal. 

Timber. 

165.  The  timber,  unless  otherwise  specified,  shall  be  Timber, 
strictly  first-class  spruce,  white  pine,  southern  yellow  pine 

or  white  oak  bridge  timber,  sawed  true,  and  out  of  wind, 
full  size,  free  from  wind  shakes,  large  or  loose  knots* 
decayed  or  sap  wood,  worm  holes,  or  other  defects  impair¬ 
ing  its  strength  or  durability.  It  will  be  subject  to  the 
inspection  and  acceptance  of  the  Engineer. 

INSPECTION. 

166.  All  facilities  for  inspection  of  the  materials  and  Inspection, 
workmanship  shall  be  furnished  by  the  contractor.  He 

shall  furnish  without  charge  such  specimens  (prepared)  of 
the  several  kinds  of  steel  to  be  used,  as  may  be  required  to 
determine  their  character. 

167.  The  contractor  must  furnish  the  use  of  a  testing 
machine  capable  of  testing  the  above  specimens  at  all  mills 
where  the  steel  may  be  manufactured,  free  of  cost. 

168.  Full  sized  parts  of  the  structure  may  be  tested  at 
the  option  of  the  Engineer,  but  if  tested  to  destruction, 
such  material  shall  be  paid  for  at  cost,  less  its  scrap  value 


28 


to  the  contractor,  if  it  proves  satisfactory.  If  it  does  not 
stand  the  specified  tests,  it  will  be  considered  rejected 
material,  and  be  solely  at  the  cost  of  the  contractor. 

PAINTING. 

Painting.  1 69.  All  metal  work  before  leaving-  the  shop  shall  be  thor¬ 

oughly  cleaned  from  all  loose  scale  and  rust,  and  be  given 
one  good  coating  of  pure  raw  linseed  oil,  well  worked  into 
all  joints  and  open  spaces. 

Buckle-plates  shall  be  given  a  thick  and  thorough  coat¬ 
ing  of  red  lead  and  linseed  oil  betore  shipment.  All  rivet 
heads  in  the  buckle-plate  floor  shall  also  be  coated  with 
this  read  lead  paint  as  soon  as  practicable  after  they  are 
driven. 

170.  In  riveted  work  the  surfaces  coming  in  contact  shall 
each  be  painted  before  being  riveted  together.  Bottoms  of 
bed  plates,  bearing-plates,  and  any  parts  which  are  not 
accessible  for  painting  after  erection,  shall  have  two  coats 
of  paint ;  the  paint  shall  be  a  good  quality  of  iron  ore  paint, 
mixed  with  pure  linseed  oil. 

1 7 1 .  After  the  structure  is  erected,  the  metal  work  shall 
be  thoroughly  and  evenly  painted  with  two  additional  coats 
of  paint,  mixed  with  pure  linseed  oil.  All  recesses  which 
will  retain  water,  or  through  which  water  can  enter,  must 
be  filled  with  thick  paint  or  some  waterproof  cement  before 
receiving  the  final  painting. 

172.  Pins,  bored  pin-holes,  screw  threads  and  turned  fric¬ 
tion  rollers  shall  be  coated  with  white  lead  and  tallow  before 
being  shipped  from  the  shop. 

ERECTION. 

Erection.  173*  The  contractor,  unless  it  be  otherwise  specified,  shall 
furnish  all  staging  and  false  work,  shall  erect  and  adjust  all 
the  metal  work,  and  put  in  place  all  floor  timbers,  guards, 
etc.,  complete. 

174.  The  contractor  shall  so  conduct  all  his  operations  as 
not  to  interfere  with  the  work  of  other  contractors,  or  close 
any  thoroughfare  by  land  or  water,  except  by  written  con¬ 
sent  of . 


29 


175-  The  contractor  shall  assume  all  risks  of  accidents  to 
men  or  material  prior  to  the  acceptance  of  the  finished 
structure. 

The  contractor  must  also  remove  all  false  work,  piling 
and  other  obstructions,  or  unsightly  material  produced  by 
his  operations. 

FINAL  TEST. 

176.  Before  the  final  acceptance  the  Engineer  may  make  Final  Test, 
a  thorough  test  by  passing  over  each  structure  the  specified 
loads,  or  their  equivalent,  or  by  resting  the  maximum  load 
upon  the  structure  for  twelve  hours. 

After  such  tests  the  structures  must  return  to  their  orig¬ 
inal  positions  without  showing  any  permanent  change  in 
any  of  their  parts. 


EXPORT  WORK. 

All  plans,  including  working  drawings,  must  be  submitted  Export  work, 
for  the  examination  and  approval  of  the  Consulting  Engineer 
before  the  material  is  ordered  or  any  work  done. 

Any  proposed  modification  of  accepted  plans,  to  adapt 
them  to  the  plant  and  methods  of  the  manufacturer  or  to 
facilitate  the  prompt  delivery  of  the  work,  must  also  be 
submitted  to  and  approved  by  the  Consulting  Engineer, 
before  such  changes  can  be  allowed. 

In  all  designs,  the  length  and  size  of  parts  must  be  so 
arranged  that  they  can  be  readily  handled  and  stored  dur¬ 
ing  transportation  to  the  site. 

Length  of  bars,  posts,  chords  and  pieces  of  small  section 
must  not  exceed . feet. 

Length  of  girders  or  girder  sections  over . feet 

in  width  must  not  exceed . feet. 

Weight  of  any  single  piece  must  not  exceed . 

pounds. 

Pins,  roller-nests,  bolts,  rivets  and  all  small  pieces  must 
be  packed  in  strong,  iron-bound  boxes,  with  the  detailed 
contents  of  each  box  legibily  marked  on  the  outside.  Boxes 
to  be  consecutively  lettered  or  numbered. 


30 


The  screw-ends  of  all  bars  to  be  securely  protected  by 
canvass  wrapped  and  wired  about  the  same. 

Every  piece  must  not  only  be  legibily  marked  by  paint, 
but  also  by  letters  stamped  on  the  metal,  showing  its  loca¬ 
tion  in  the  structure. 

All  necessary  rivets  for  the  field  connections,  with  an 
extra  allowance  of  25  per  cent,  for  each  kind,  shall  be  sent 
with  each  shipment. 

The  customary  pilot-nuts  (§  146)  for  all  pins  shall  be  sent 
with  the  pins. 


SUPPLEMENTARY. 

The  following  special  clauses  shall  apply  in  addition  to 
previous  general  clauses,  to  the  special  work  included  in 
the  attached  contract : 


31 


GENERAL  DATA. 


For  a  bridge  crossing _ _ _ _ in  the  town 

of . .  .County  of _ State  of 


. . to  be  built  according  to  the  general 

requirements  of  the  accompanying  specifications: 

Width  of  roadway . . . . . 

Number  of  footwalks . . . . . 

Width  of  footwalks _ _ _ _ 

Kind  of  floor  or  paving . . . . 

Number  of  car  tracks . 

Spacing  “  “  . . . 

Height  of.floor  above  flood  line _ 

Height  of  floor  above  ordinary  stage  of  water . . 

Depth  of  river  at  ordinary  stage  of  water . . . . 

Character  of  river  bed _ _ _ 

Usual  seasons  for  floods _ _  _ _ 

Length  of  haul  from  nearest  freight  station _ _ 

Specified  live  load,  Class  Ai,  A2,  B,  C,  D,  Ei  or  E2,  para¬ 
graph  38,  to  be  adopted  for  this  bridge _ 

Sizes  of  piers  (if  built  or  contracted  for).. . . . 

Skew  of  piers,  or  angle  of  current  with  line  of  the  bridge. 

Total  length  of  bridge _ _ _ _ _ _ _ 

Length  of  spans  centre  to  centre  of  piers . .  . . 


APPENDIX. 


34 


TABLE  I. 

Maximum  End  Shears  S,  Moments  31,  and  Reactions  R  for  Live 
Loads  (only),  on  Stringers  and  Eloor-Beams  of  Class  Ex. 


Span. 

Each  stringer. 

Floor-Beams. 

Single  track. 

Double  track. 

L. 

S. 

M. 

Least 

R. 

M. 

R. 

M. 

Ft, 

Lbs. 

1  uuu 
inch-lbs. 

size. 

Lbs. 

Lbs. -ft. 

Lbs. 

Lbs. -ft. 

10 . 

12  000 

360 

12  000 

24  000 

11 . 

13  100 

396 

12-in.  I. 

12 . 

14  000 

432 

13 . 

14  800 

468 

14 . 

15  400 

504 

15 . 

16  000 

540 

10 . 

16  500 

576 

17 . 

16  900 

612 

| 

18 . 

17  300 

676 

15-in.  I. 

1 

1 

19 . 

17  700 

743 

[S 

1 

20 . 

18  000 

810 

• 

21 . 

18  300 

878 

22 . 

18  500 

946 

II 

1 

« 

23 . 

18  800 

1  014 

18-in.  I. 

II 

II 

II 

ll 

24 . 

19  000 

1  083 

03 

!a 

03 

25 . 

19  200 

1  152 

20 . 

19  400 

1  221 

27 . 

19  600 

1  291 

20-in.  I. 

28 . 

19  700 

1  360 

19  900 

1  430 

30 . 

20  000 

1  500 

20  000 

40  000 

Moment  for  stringers  equals 

pi 

M  =  —  up  to  17  feet. 
n _ 5)2 

M  =  P  — — —  over  17  feet,  in  foot-pounds. 

S  —  end  shear  of  one  stringer. 

M—  maximum  moment. 

P  =  concentrated  load  on  one  wheel. 

I  —  span  in  feet. 

d  =  distance  in  feet,  center  to  center  of  trusses, 
e  =  distance  in  feet,  center  to  center  of  tracks. 
f  =  “  “  “  '  “  stringers. 


10. 

11. 

12. 

13. 

14. 

15. 

16. 

17, 

18. 

19. 

20. 

21. 

22, 

23. 

24, 

25. 

26. 

27. 

28. 

29. 

30. 


35 


TABLE  II. 
Same  for  Class  E2. 


Each  stringer. 

8. 

Lbs. 

M. 

1  000 
incb-lbs. 

Least 

size. 

9  000 

270 

10-in.  I. 

9  800 

297 

10  500 

324 

11  100 

351 

11  600 

378 

12-in.  I. 

12  000 

405 

12  400 

432 

12  700 

459 

13  000 

507 

13  300 

557 

13  500 

607 

13  700 

658 

15-in.  I. 

13  900 

709 

14  100 

761 

14  200 

812 

14  400 

864 

14  500 

916 

18-in.  I. 

14  700 

968 

14  800 

1  020 

14  900 

1  073 

15  000 

1  125 

20-in.  I. 

Floor-Beams. 


Single  track. 

Double  track. 

R.  ■ 

M. 

R. 

M. 

Lbs. 

Lbs.  ft. 

Lbs. 

Lbs.  ft. 

- 

Q 

✓—v 

I 

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1 

2d 

2 Q  |(N 

2Q 

II 

II 

II 

ii 

0$ 

TABLE  ill. 

Maximum  End  Shears*  S,  Moments  M  and  Beactions  R  fcr  Live  Loads  (only)  on  Stringers  and  Floor-Beams 

of  Classes  A  and  B,  with  Double-Track  Railway. 


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